test: Update OIDC integration test

[labrenbe]

Description

Part of https://github.com/stackabletech/druid-operator/issues/473

Update the OIDC integration test to do a full OIDC login flow and check that data ingestion is not broken.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [ ] Changes are OpenShift compatible
- [ ] CRD changes approved
- [ ] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [ ] Helm chart can be installed and deployed operator works
- [ ] Integration tests passed (for non trivial changes)
- [ ] Changes need to be "offline" compatible

# Reviewer
- [ ] Code contains useful comments
- [x] (Integration-)Test cases added and/or extended
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added
- [ ] [Roadmap](https://github.com/orgs/stackabletech/projects/25/views/1) has been updated

[sbernauer]

@labrenbe the nightly tests are failing wuth KeyError: 'DRUID_OIDC', do you mind having a look? https://ci.stackable.tech/view/01%20Operator%20Tests%20(nightly)/job/druid-operator-it-nightly/520/